120 



rally called light hydrocarbonate, is in reality a mere mixture of hy- 

 drogen and olefiant gases. In proof of this opinion he details a series 

 of analytical experiments upon the gases from coal, oil, acetate of 

 potash, moist charcoal, &c., conducted chiefly by detonation with 

 oxygen, by heat alone, and by the action of sulphur at high tempe- 

 ratures, and obtains results analogous to those afforded by mixtures 

 of hydrogen and olefiant gas, of the same specific gravities. Of 

 the gases above-mentioned, however, the specific gravity, combusti- 

 bility, and intensity of light during combustion, are often much in- 

 terfered with by the presence of carbonic oxide and carbonic acid. 



Of the products obtained by the destructive distillation of coal and 

 oil, Mr. Brande thinks that some are of what may be termed secon- 

 dary formation ; that is, that they result from the mutual action of 

 the first formed gaseous products at high temperatures. Thus a 

 peculiar compound of hydrogen and carbon, volatile and odorous, re- 

 sembling tar in appearance, but having the characters of resin, is 

 formed by passing pure olefiant gas through a tube of red-hot 

 charcoal ; and sulphuret of carbon is formed by the mutual agency of 

 carburetted and sulphuretted hydrogen gases at high temperatures. 

 To the latter compound the author refers the production of sulphu- 

 rous acid, by the combustion of coal gas in cases where, by the test 

 of acetate of lead, it is shown to be free from sulphuretted hydrogen. 

 In this section of the paper the author further details some pro- 

 cesses for the analysis of complex gaseous mixtures, which he thinks 

 afford more accurate results, and are easier of performance than 

 those usually practised, and which are rendered important as eluci- 

 dating the nature of the gaseous products, now in common use for 

 artificial illumination. 



The second section of this lecture contains comparative experi- 

 ments on the heating and illuminating powers of olefiant, coal, and 

 oil gases, with some incidental remarks on the general properties of 

 radiant matter. 



To give the light of ten ordinary wax candles for one hour it re- 

 quired 2600 cubic inches of olefiant gas, 4875 of oil gas, and 13,120 

 of coal gas. The consumption of oxygen amounts in the first to 

 7800 cubic inches, in the second to 11,578 cubic inches, and in the 

 third to 21,516 ; hence it follows that the heating powers of the re- 

 spective flames being nearly similar, there will necessarily be much 

 more heat produced by coal gas illumination than by an equal illu- 

 mination of oil gas, and by oil gas more than by olefiant. 



The economy of combining several flames for the production of 

 light is strikingly illustrated by comparative experiments upon in- 

 sulated and combined jets of flame. Thus, in respect to olefiant gas, 

 a single jet, producing the light of one candle, consumes 640 cubic 

 inches per hour; while a burner, with united jets of flame, giving the 

 light of ten single jets, consumes only 2600 cubic inches, instead of 

 the estimated quantity of 6400. 



Some comparative experiments upon the effects of solar and ter- 

 restrial light conclude this lecture, from which it appear? that, al- 



